Modeling composition

ABSTRACT

Thermoplastic modeling compositions which are resistant to cracking on standing after they have been molded. Preferably lightweight, they are relatively soft and easily molded at elevated temperatures and are slump or distortion-resistant but still pliable and finger-pressure deformable at room temperature. Distributed throughout the modeling compositions are rigid, regularly shaped microparticles, e.g., in the form of spheres or platelets.

United States Pniani Harold T. Wmgiield Birchwood, Minn.

Mar. 20, 1968 Sept. 21, 1971 Minnesota Mining and Manufacturing lCompanySt. Paul, Minn.

App]. No. Filed Patented Assignee MUDELWG CUMPOSIITIION 7 Claims, NoDrawings 11.8.Cl 106/243, 106/266, 106/268, 106/272 ]lnt. iC ll 08119/00 [5 0] liielld all Search Primary Examiner-Lorenzo B. HayesAttorney-Kinney, Alexander, Sell, Steldt & Delahunt ABSTRACT:Thermoplastic modeling compositions which are resistant to cracking onstanding after they have been molded. Preferably lightweight, they arerelatively soft and easily molded at elevated temperatures and are slumpor distortion-resistant but still pliable and finger-pressure deformableat room temperature. Distributed throughout the modeling compositionsare rigid, regularly shaped micropartil cles, e.g., in the form ofspheres or platelets.

MODELING COMPOSITION BACKGROUND OF THE INVENTION 1. Field of theInvention This invention relates to thermoplastic modeling compositionswhich are resistant to cracking and preferably lightweight. Thecompositions of the invention are plastic and moldable at elevatedtemperatures and more rigid and slump or distortion-resistant but stillpliable and finger-pressure deformable at room temperature Distributedthroughout the modeling compositions are rigid regularly shapedmicroparticles, e.g., in the form of spheres or platelets, the preferredform being rigid hollow microbubbles. Microparticles are herein defined500 microns or smaller in size.

2. Description of the Prior Art It has been the practice in the stylingand industrial design trades, particularly in the automotive industry,to construct full scale, detailed models or prototypes with modelingclays prior to manufacturing the marketable product. Often thesemodeling clays or compositions are thermoplastic and comprise a mixtureof sulfur, naturally occurring clays, crystalline aliphatic esters andfatty acids. Normally they are heated until pliable and applied to ageneralized outline of the model called a buck, which is a structuralmaterial such as wood, and formed thereon while the clay is still warmand pliable. As the clay prototype is cooled to room temperature, itbecomes more rigid and loses much of its plasticity. In the case of anau' tomobile prototype, for example, the clay is distributed unevenly onthe buck and its thickness may vary from thin layers of one-fourth inchto thicker layers of 8 to 12 inches. A finished automobile prototype soconstructed may weigh as much as 5000 pounds and the modeling clayemployed will normally exhibit several cracks or fissures after a periodof about 24 hours. Such cracks tend to weaken the structural integrityof the model and detract from its aesthetic qualities; furthermorecontinued repair of such cracks is time consuming. Since the clayprototypes are commonly used as models for making plaster or fiberglasscasts, the cracking occurring in the clay prototype within a relativelyshort period of time is particularly undesirable since the cast must bemade quickly, before cracks occur, thus requiring minor stylingmodifications to be made in haste.

Accordingly, it is an object of the present invention to provide amodeling composition which is resistant to cracking on standing andpreferably lightweight, and which is relatively soft and easily moldedat elevated temperatures while being slump or distortion-resistant butstill pliable and finger-pressure deformable at room temperature.

Other objects and advantages will become evident from the followingdetailed but nonlimiting DESCRIPTION OF Til-IE INVENTION It has beenfound that on intimate mixture of a plastic, claylike mass, comprisingfinely divided filler material, at least a portion ofwhich being clayand a plasticizing organic vehicle for said filler material; togetherwith from about to about 50 volume percent of rigid, regularly shapedmicroparticles, provides a thermoplastic modeling composition whichaccomplishes the above noted objects. The microparticles used in thepractice of the invention are preferably hollow microspheres, but mayalternatively be in the form of tiny platelets or microcyiinders.

The physical properties of the modeling compositions of the presentinvention may be adjusted to suit the need of the user by varying thequantities and types of filler, vehicle and microparticles employed.Thus fillers may be selected from finely divided, particulate materialssuch as are often found in known modeling compositions. In order toprovide a composition which is deformable, yet has the desired cohesivestrength, the filler selected should include a portion of clay. By clayis meant either naturally occurring clays such as kaolinite,montmorillonite or bentonite, as well as modified clays such as aminemodified bentonite, known commercially under the trade name Bentones,"which are reaction products of cation exchange reactions between organicbases and bentonite and have a platelet-type structure.

Other finely divided filler materials having relatively high softeningand melting points, preferably higher than 150 F., such as sulfur,calcium carbonate, and zinc stearate are mixed with the clay inproportions to give the composition the desired consistency andworkability. A particularly suitable filler comprises l530 weightpercent sulfur, 40-80 weight percent clay, and 15-30 weight percent zincstearate. Further, while it is to be understood that the amount offiller employed in the final modeling composition may be varied to suitthe needs of the user, preferred modeling compositions of the inventioncontain from 40 to 60 weight percent filler material.

The claylike mass further includes a thermosoftening, plasticizingvehicle for lubricating and binding the filler material. Oils, waves andgreases, or mixtures thereof such as are commonly found in knownmodeling compositions are acceptable. Solids contained in the vehicleshould melt or soften between F. and 175 F., preferably between q F. andF. and should not react chemically to produce a permanent phase change.By variation of the amount and type of vehicle employed, the physicalproperties of the composition can be altered so as to effect specificconsistency and workability requirements. Suitable vehicles may includethe following materials and mixtures thereof: oils, such as glycerin,fatty acids, polymerized fatty acids, rosin oils, palm oils; greasessuch as lanolin, petrolatums, tallow; and thermoplastic solids such asparaffin waxes, beeswax and crystalline aliphatic esters.

Preferred vehicles include approximately 30 to 75 weight percent dimerand trimer acids, e.g., those derived from wood rosin; approximately 0to 45 weight percent of lanolin or glycerin and approximately 20 to 40weight percent of hydrocarbon wax, e.g., paraffin.

Preferred modeling compositions of the invention include from about 10to about 50 volume percent of regularly shaped microparticulate materialwhich effects a distinct resistance to cracking in the compositions instanding after it has been molded. Preferably, the microparticles arerigid, hollow microbubbles (e.g., as described in US. Pat. 3,365,315,Beck et al., issued Jan. 23, 1968) so as to further effect a significantreduction in density which improves the slump resistance of thecomposition. It has been found that the use of amine modified clays, asdescribed above, also improves the resistance to cracking of thecompositions in addition to the improvement provided by themicrobubbles. When naturally occurring clays such as kaolinite,bentonite and montmorillonite are employed as the clay portion of thetiller, it is preferable that the glass microbubbles be first treatedwith a glass surface treatment (e.g. a glass coupling agent) in order toeffect a resistance to cracking comparable to that provided by the useof untreated microbubbles in combination with amine-modified clays.

Depending on the consistency of the composition desired, suitablemicrobubbles may be selected within a diameter range of the order of 5to 300 microns. In cases where a smooth consistency into modelingcomposition is not required, microspheres of larger diameters may beemployed. Preferred microbubbles are those having average diameters ofbetween 10 and 150 microns since those with diameters above 150 micronsimpart a somewhat coarse consistency to the composition. Particularlypreferred for automobile prototype styling and the like are microbubbleshaving diameters of between 10 and 100 microns. When modelingcompositions of significantly reduced density are desired microbubbleshaving densities of the order of 0.10 to 0.60 g./cc. are acceptablewhile those with densities of from 0.20 to 0.40 g./cc. are preferred.

As noted above, when glass microspheres are employed in compositionshaving naturally occurring clays as the clay portion of the tiller, themicrospheres should be preliminarily treated with a glass surfacetreatment. Suitable or this purpose is a glass coupling agent consistingessentially of an aqueous solution of a Werner-type compound such as achrome complex of methacrylic acid. Other glass coupling agents such asorgano silane compounds will be evident to those skilled in the art.

Further examples of microspheres which are effective in reducingcracking in modeling compositions are hollow glass microbubbles, solidglass microspheres, solid epoxy microspheres, expanded polystyrenespheres, and phenolic microbubbles. Platelet-type microparticles such asexpanded vermiculite are also effective to reduce cracking.Alternatively, microcylinders, such as those obtained from short lengthmicrofibers could be employed. As noted above, hollow microparticles areemployed in preparing the preferred low density modeling compositions.

While noncracking modeling compositions of the invention may includefrom about to about 50 volume percent of microspheres, preferredcompositions are those which include to 40 volume percent microspheres.The inclusion of such a volume percent of microbubbles effects areduction in density of 13-27 percent when microbubbles of a density of0.35 g./cc. are employed and substantially reduced cracking in the finalmodeling composition. Modeling compositions including greater than 50volume percent microspheres generally are short, coarse and have littlecohesive strength although the composition may be modified to remedythese shortcomings, while those including less than 10 volume percentare not preferred since at these low percentages cracking in themodeling composition is not sufficiently reduced.

Preferred embodiments of the invention, particularly useful, forexample, in automobile prototype styling, include the following weightpercentages of fillers, vehicle and microspheres wherein clay forms atleast 10 percent of the composition.

modeling 40-60 vehicle 30-45 micrcspheres 20-40 In addition, modellingcompositions of the invention may optionally include coloring agents orthe like. Pigments such as chrome oxide, carbon black, oil ground chromeyellow or the like are preferred to dyes since they do not stainmaterials with which they come into contact.

The following examples are provided as being illustrative of specificpreferred embodiments of the invention. They are not to be considered aslimiting the scope of the invention.

DESCRIPTION OF TEST FOR DETERMINING THE AMOUNT AND DEGREE OF CRACKING30-35 cc. f the modeling composition to be tested were molded on one endof a 5-6 inch X ll/2 inch X 3/4 inch piece of wood in the form of a drumstick. The modeling composition was molded to cover approximatelyone-half the length of the stick and extended over the end thereof byapproximately one-half inch. Absorptive paper toweling was placed overthe exposed portion of the wood and the entire piece soaked with water.Both pine and mahogany woods were used and the sticks were cut with thegrain of the wood running parallel to the length thereof. Measurementstaken of the sticks before and after water soaking indicated an areaexpansion of approximately 5.5 percent across the grain. Densitymeasurements of the modeling compositions were determined with an aircomparison Pycrometer. Lightweight modeling compositions were defined ashaving densities of Li g./cc. or less:

EXAMPLE I A. Two batches of modeling compositions were formulated havingweight percent compositional analyses as follows:

Both compositions were mixed in a small sigma blade mixer heated to130F., with hot water. The beeswax was charged into the mixer after it hadmelted, the remaining components being then added and mixed thoroughlyfor one hour. Composition A was relatively short, crumbly and of lowcohesive strength. Composition B was of suitable consistency as amodeling composition. Both compositions were subjected to the abovedescribed cracking test. Both compositions exhibited several crackswithin 2 hours. Both were severely cracked after 3 days.

B. A modeling composition of similar compositional analysis tocomposition B above, except microbubbles treated with a Werner-typeglass coupling agent were added. The weight percent compositionalanalysis was as follows:

COMPOSITION C Weight Sulfur ll.l Weight Kaolin 40.3 Weight Beeswax 9.8

weight Dimer acid (Empol lOlO) Weight Zinc stearate Weight Glassmicrobubbles (Average bubble density of().35; average bubble diameter of20-80 microns) Density (g/CC.)

The composition was of good workable consistency. After being subjectedto the cracking test for 3 days only one hairline fissure one-eighthinch long was observed.

EXAMPLE II Four compositions were formulated, all containing Weight i;lanolin Weight paraffin wax Weight dimer acid (Empol i010) Weight zincstearate Weight 70 bentonite Weight k sulfur Weight '1. microbulloomiWeight '5 flake graphite weight 70 Bentonc l 1 Density g./cc.

l2.9 20.7 l4.3 l4.7

10.4 9.8 1L4 ll.7

ll.) M2

All of the compositions exhibited properties which made them acceptableas modeling compositions. All were easily worked V and modeled at 125 F.and became more rigid and distortion- EXAMPLE Ill A compositioncontaining solid glass beads having an average particle density of 2.5g./cc. and an average particle diameter of from 30 to 38 microns wasformulated comprising the following weight percent compositionalanalysis:

Weight paraffin wax 6.6 Weight 56 lanolin 6.7 Weight 5k dimer acid(Empol i010) 7.9 Weight zinc stearate 6.2 Weight 1: Bentone H 10.9Weight sulfur 7.5 Weight glass beads 54.2 Density 1.6 g./cc.

The resulting modeling composition was subjected to the cracking test.After 6 hours, no cracks appeared. After 3 days, a few short hairlinecracks were observed.

EXAMPLE IV A composition containing expanded polystyrene beads having anaverage particle density of 0.12 g./cc. and diameters ranging between590 and 840 microns was formulated comprising the following weightpercent compositional analysis:

Weight 11 paraffin wax 13.7 Weight lanolin 13.9 Weight I: Dimer acid(Empol ll0) 16.3 Weight 91 Zinc stearate l2.9 Weight Bentone H 22.2Weight sulfur 15.6 Weight k expanded polystyrene heads 5.4 Density 0.9g./cc.

Although the resulting composition exhibited a coarse and grainyconsistency and a smooth surface finish could not be obtainedexamination of the formed sample after 3 days exposure to the crackingtest revealed that no cracking had occurred.

What I claim is:

l. A thermoplastic modeling composition, substantially free of volatileconstituents, having plastic and moldable properties at temperatures ofthe order of q F. to 150 F. so as to be relatively soft and easilymolded at said temperatures and being more rigid andslump or distortionresistant but still pliable and finger-pressure deformable at roomtemperature, said composition of matter comprising an intimate mixtureof a plastic-claylike mass comprising: finely divided particulate solidfiller, at least 10per cent by weight of which is clay, together with athermoplastic plasticizing organic vehicle therefor and havingdistributed therethrough between about 10 and 50 volume percent of rigidmicroparticles of predetermined regular shape and size, said compositionbeing resistant to cracking on standing after it has been formed. 2. Thecomposition of claim 1 wherein said claylike mass has a weight percentcompositional analysis comprising the following:

finely divided solid inorganic filler including finely divided clay 10to 50 sulfur 0 to 40 Plasticizing organic vehicle including:

hydrocarbon waxes 3 to 20 oils 5 lo 25 greases 0 to 20 wherein said clayis selected from the group consisting of naturally occurring clays andthe reaction products resulting from cation exchange reactions betweenorganic bases and montmorillonite and wherein solid components of saidplasticizing organic vehicle have melting or softening points of theorder of F. to 175 F.,

wherein said regularly shaped rigid microparticles are selected from thegroup consisting of rigid, hollow microbubbles, solid microspheres,platelet shaped particles, and microcylinders.

3. The composition of claim 2 wherein said regularly shapedmicroparticles are rigid, hollow microbubbles having an average bubblediameter of the order of 5 to and having an average bubble density orthe order of 0. 10 to 0.6 g./cc.

41. The composition of claim 3 wherein the microbubbles have averagedensities of the order of 0.20 to 0.40 g./cc.

5. The composition of claim 3 wherein said rigid, hollow microbubblesare glass and have been treated with a glass treatment agent.

6. The composition of claim 5 wherein the flask treatment agent isselected from the group consisting of glass coupling agents of theWerner complex-type and organosilane compounds.

7. A thermoplastic light weight modeling composition, having plastic andmoldable properties at temperatures of the order of 100 F. to 150 F. soas to be relatively soft and easily molded at said temperature and beingmore rigid and slump or distortion-resistant but still pliable andfinger-pressure deformable at room temperature comprising an intimatemixture of the following components: lanolin, dimer acid, zinc stearate,reaction products of cation exchange reactions between organic bases andbentonite, sulfur, and between about 10 and 50 volume percent of rigid,hollow microbubbles having average diameters of the order of 10 150microns and average densities of the order of 0.0[10 to 0.60 microns andaverage densities of the order of 0.10 to 0.60 g./cc., said compositionbeing resistant to cracking on standing after it has been molded.

UNITED STATES PATENT OFFICE CERTIFEQATE 0F ORRETION Patent No. 3,607,332Dated September 21, 1971 Inventor(s) Harold T. Wingfield It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 1, line 13, after "temneratur'e insert Column 2, line 25, deleteE P." and insert --100 F.

Column 3, line A l, delete modeling and insert --f-illers--;

line 57, after "cc." delete "f" and insert -of-.

Column 5, line 59, delete l fF." and insert --l00 F.--.

Column line 3?, aft-er "150" and before "and" insert --microns--; line&4, delete "flask" and insert --glass--; line 59, delete the phrase"average densities of the order of 0.010 to 0.60 microns and".

Signed and sealed this 25th day of A i 1972.

(SEAL) Attest:

EDWARD 1..FLETCH1H,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents ORM PC3-1050 (10-69) uscoMM-oc 60376-P6Q Q u.5 GOVERNMMHPRINTING OFFiCE: 1969 O365.IJ

2. The composition of claim 1 wherein said claylike mass has a weightpercent compositional analysis comprising the following: finely dividedsolid inorganic filler including finely divided clay 10 To 50 sulfur 0to 40 Plasticizing organic vehicle including: hydrocarbon waxes 3 to 20oils 5 to 25 greases 0 to 20 wherein said clay is selected from thegroup consisting of naturally occurring clays and the reaction productsresulting from cation exchange reactions between organic bases andmontmorillonite and wherein solid components of said plasticizingorganic vehicle have melting or softening points of the order of 100* F.to 175* F., wherein said regularly shaped rigid microparticles areselected from the group consisting of rigid, hollow microbubbles, solidmicrospheres, platelet shaped particles, and microcylinders.
 3. Thecomposition of claim 2 wherein said regularly shaped microparticles arerigid, hollow microbubbles having an average bubble diameter of theorder of 5 to 150 and having an average bubble density or the order of0.10 to 0.6 g./cc.
 4. The composition of claim 3 wherein themicrobubbles have average densities of the order of 0.20 to 0.40 g./cc.5. The composition of claim 3 wherein said rigid, hollow microbubblesare glass and have been treated with a glass treatment agent.
 6. Thecomposition of claim 5 wherein the flask treatment agent is selectedfrom the group consisting of glass coupling agents of the Wernercomplex-type and organosilane compounds.
 7. A thermoplastic light weightmodeling composition, having plastic and moldable properties attemperatures of the order of 100* F. to 150* F. so as to be relativelysoft and easily molded at said temperature and being more rigid andslump or distortion-resistant but still pliable and finger-pressuredeformable at room temperature comprising an intimate mixture of thefollowing components: lanolin, dimer acid, zinc stearate, reactionproducts of cation exchange reactions between organic bases andbentonite, sulfur, and between about 10 and 50 volume percent of rigid,hollow microbubbles having average diameters of the order of 10 150microns and average densities of the order of 0.010 to 0.60 microns andaverage densities of the order of 0.10 to 0.60 g./cc., said compositionbeing resistant to cracking on standing after it has been molded.